Core-spun yarns,fabrics and process for the preparation thereof



United States Patent 3 487,628 CORE-SPUN YARNS FABRICS AND PRUCESS FOR THE PREPARATION THEREOF Tiber Csolr, Chadds Ford, Pa, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del, a corporation of Delaware No Drawing. Filed Sept. 30, 1966, Ser. No. 583,439 Int. Cl. D02g 3/36 US. Cl. 57152 11 Claims ABSTRACT OF THE DISCLOSURE Core-on-core spun yarns having an elastic continuous filament core, a first core-spun sheath of inelastic staple fiber surrounding the plastic core in a series of turns, and a second core-spun shealth of inelastic staple fiber surrounding portions of the first sheath in a series of turns of opposite spiral disposition. The fibers used in each corespinning preferably are of different properties (e.g., dyeability) and such yarns are useful in preparing fabrics with unusual properties.

This invention is concerned with the production of novel yarns and fabrics. It is particularly concerned with the production of novel core-spun yarns of spandex and inelastic fibers.

Core-spun yarns from spandex or other elastic fibers with inelastic fibers are well-known articles of commerce. Yarns of various degrees of stretch, bulk, stretch modulus and other properties are made by this route. Some of this art is disclosed in US. Patents 3,009,311 to Wang, 3,017,740 and 3,038,295 to Humphreys. However, it ap pears not to have been discovered heretofore that great improvements in fabric aesthetics can be obtained by core-on-core spinning which is the subject of the present invention.

In carrying out this invention, a elastic yarn is provided comprising continuous filament elastic fiber used as the core and a composite sheath made up of two inelastic fibers preferably of different properties.

The elastic yarn of the invention comprises an initially stretched elastic core of one or more elastic continuous filaments, preferably spandex filament. A first sheath consisting of inelastic staple fiber roving(s) surrounds the elastic core in a series of turns (either S or Z twist). A second sheath consisting of inelastic staple fiber roving(s), preferably having properties which differ from those of fiber in the first sheath, surrounds the elastic core and 0 portions of the first sheath in a series of turns in the opposite spiral disposition (ie, if the twist of the first sheath is S twist, the twist of the second sheath is Z twist, and vice versa). The two sheaths are further characterized by having portions of the first sheath not completely covered by the second sheath, preferably turns or loops of the inelastic fibers of the first sheath will come through to the surface of the second sheath. When the dyeability properties of the fibers differ substantially, cross-dyeing is made possible. It is preferred that in the final yarn the second sheath have a number of turns per inch approxi mately equal in number, although opposite in direction, to the turns per inch of the first sheath. This provides a balanced yarn with little tendency to untwist.

The process of this invention comprises a core-on-core spinning to provide an elastic yarn. An elastic core of at least one elastic continuous filament is stretched. The stretched core is core-spun with a first inelastic staple fiber roving(s) to provide a yarn having a series of turns (either S or Z twist). Thereafter the core-spun yarn is again core-spun (ie, core-on-core spun) with a second inelastic staple roving(s) preferably having different propice erties eg, dyeability from that of the first inelastic staple fiber roving(s). This second core-spinning provides twist in the opposite spiral configuration to that provided by the first core-spinning. It is preferred that the second core-spinning provide a lesser amount of twist than the amount provided in the first core-spinning. This is preferred because the first sheath is untwisted to a certain extent during the second core-spinning. The relative number of turns in each core-spinning is preferably adjusted to compensate for such untwisting and to provide a balanced yarn i.e., in the final yarn each sheath has approximately the same number of turns per inch although the twists are in opposite directions.

As used herein, the term core-spinning refers to the process of introducing continuous filament to a conventional spinning or drafting frame together with one or more rovings of staple fibers so that a composite yarn is formed in which the continuous filament is a core about which is spun a sheath of drafted staple fibers.

The term core-on-core" refers to a second core-spinning i.e., core-spinning a yarn which has previously been core-spun. The term is distinct from a single core-spinning using two or more rovings (although using two or more rovings in each core-spinning is within the scope of the practice of this invention).

The term elastic fibers refers to synthetic and natural fibers having a high breaking elongation e.g., 100 percent or more, preferably 500 percent to 800 percent, and a low elastic or initial modulus e.g., less than one gram per denier, preferably 0.08 gram per denier or lower, and exhibit a quick and substantially complete recovery from stretching to an amount less than their breaking elongation, e.g., having a tensile recovery of about percent or more and a stress decay of less than about 20 percent.

The term inelastic fibers refers to natural and synthetic fibers which generally have a breaking elongation of less than about percent and, as compared to elastic fibers, have a relatively high elastic or initial modulus, e.g., from 4 to 100 grams per denier or greater.

The preferred elastic fibers of this invention are spandex fibers which are filaments composed of at least 85 percent of segmented polyurethane further characterized by having segments of high-melting crystalline polymer alternating with segments of low melting amorphous polymer. Segmented elastomers of this type and processes for preparing them in filamentary form are described in US. Patents 2,813,775, 2,813,776, 2,929,800, 2,929,801, 2,929,804, 2,953,839, 2,957,852, 3,097,192, 3,077,006, in British Patent 779,054, and in French Patent 1,388,558 to which reference can be made for details.

The preferred inelastic fibers of this invention are the acrylic and modacrylic fibers but polyamide, polyester, polyacetal or the natural fibers may also be used. By varying the combinations of inelastic fibers, yarns of different bulk, different dyeing characteristics, different luster and other variations can be produced. Thus, one may use an acid dyeing fiber for one sheath and a basic dyeing fiber for the other; or a non-dyeable fiber for one and a dyeable fiber for the other. It is also possible to use a basic dyeable polyester fiber and an acid dyeable polyamide fiber for cross-dyeing effects.

The acrylic fibers are especially suitable for use in this invention because they are readily available in non-staining, acid dyeable, or basic dyeable form; with low or high shrinkage; and with self-crimping properties. The acrylic fibers also offer the advantage of being more woollike and possessing the aesthetic properties which are desirable in sweaters, dresses, and suits.

A wide range of turns per inch may be provided in each core-spinning, preferably from about 6 to about 20 turns per inch twist in the first core-spinning and preferably from about 3 to about 10 turns per inch twist in the second core-spinning. As previously stated, the yarn twist should generally be higher in the first core-spinning and in opposite direction from that in the second core-spinning in order to give a balanced yarn. Although an unbalance, which tends to untwist the yarn, can be corrected by heat-setting operations in many instances, a balanced yarn is preferred. However, for example, if only thermoplastic fibers are used, the liveliness of the yarn can be controlled, if desired, by heat-setting the final yarn.

When in the first core-spinning, the sliver of inelastic fiber is twisted about 12 Z turns per inch and then corespun with a sliver of inelastic fiber and twisted about 6 S turns per inch a suitable balanced yarn is obtained. This second core-spinning partially untwists the first corespun yarn with the result that turns o-r loops of the inelastic fibers of the first core-spun yarn come through to the surface of the final yarn.

By varying the denier of the elastomeric fiber and the weight of sliver of inelastic fibers, the proportion of elastic fiber in the final yarn, as well as the stretch modulus of the yarn, can be varied over a wide range. The elastic core generally comprises about 0.5 to about 10.0 percent by weight of the final yarn (generally from about 0.5 to about 1.5 percent is preferred). An amount of stretch of the final yarn in the range from about 50 to about 200 percent generally provided (from about 75 to about 125 percent is preferred).

The proportion of inelastic fibers in each core-spinning may also be varied over a wide range. However, the peripheral surface to be covered is greater for the second core-spinning than the peripheral surface to be covered in the first core-spinning (i.e. the peripheral surface of the yarn comprising a core and a first sheath is greater than the peripheral surface of the core itself). Since the peripheral surface varies with the square of the radius of the yarn, if an equal amount of inelastic fibers used in the second core-spinning a lesser degree of cover (compared to the covering of the first core-spinning of the core itself) would be realized. As previously discussed, having turns or loops of the first sheath come through to the surface of the second makes cross-dyeing possible. By varying the relative proportion of inelastic fiber in each core-spinning a wide variety of effects can be obtained. Approximately equal amounts of inelastic fiber in each core-spun sheath give suitable results, however varying the proportions to about 2:1 or 3:1, or even higher, also gives suitable results. The proportion chosen will depend upon the desired effect and amount of cover of the first sheath that is desired. The amount of cover also may be varied by the alignment of the core in the spinning frame and the relative amounts of twist applied in each core-spinning.

It will thus be seen that a large number of variations is possible without departing from the invention and this variability is one of the advantages of the invention. The following examples will illustrate only a few of the means of carrying out the invention.

EXAMPLE I A composite fiber is spun with polyacrylonitrile as one component and a terpolymer of 93.6 percent acrylonitrile, 6.0 percent methyl acrylate and 0.4 percent sodium styrenesulfonate as the other component. The composite fiber is spun from a solution in dimethylformamide using the technology disclosed in Breen US. Patent 3,038,236 and Kovarik US. Patent 3,038,240. After washing in hot water to remove solvent, the fibers are drawn to 1.79 times the spun length. The drawn fibers are of 6 denier per filament.

A tow of 470,000 denier of these fibers is cut on a Pacific Converter to a varicut length of 2.5 to inches (6.35 to 12.7 cm.) and the resulting sliver is pin-drafted with six passes through the pin drafter. This sliver is referred to as Sliver A. These fibers are dyeable with basicdyes.

Sliver A is next core-spun with a 40 denier spandex continuous filament fiber with a draft of 3.5 to a yarn with 12.0 Z turns per inch (3.8 turns per cm.) and a cotton count of 15/ ICC (354 denier). This yarn is wound onto perforated tubes at the spinning tension and heat-set 10 minutes at 116 C. This yarn is coded Intermediate Yarn 1.

Another sliver is prepared in the same way from fiber spun from the following terpolymer: 1

Parts Acrylonitrile 89.6 Methyl acrylate 5.7 2-methyl-5-vinylpyridine 4.7

After washing and drawing, the fiber denier is 8.5. It is cut on a Beria cutter to a varicut length of 2.5 to 5 inches (6.35 to 12.7 cm.) and carded on the worsted system. The resulting sliver is pin-drafted with six passes through the pin drafter. This sliver is coded Sliver B. These fibers are dyeable with acid dyes.

Intermediate Yarn 1 is now core-spun with Sliver B to a 6.7 cotton count (788 denier) yarn with a twist of 6 S turns per inch (2.4 turns per cm.). The amount of Sliver B core-spun is approximately equal in weight to that of Sliver A. This is coded Yarn 1.

Yarn 1 is knit on an 8-cut Cal Machine with a linksand-links stitch. The resulting fabric is steamed then dyed in a paddle dye machine with the following combination of acid and basic colors:

0.100% Du Point Anthraquinone Blue 2 GAN Color index Acid Blue 58. 0.030% Du Pont Milling Orange R 22, 195. 0.015% Du Point Azo Eosine 2B Acid Red 113. 0.180% Pontacyl LT Yellow GX 18, 965. 2.100% Sevron Brilliant Red 46..... Basic Red 14. 2.100% Sevron Blue 2G Basic Blue 22. 0.260% Sevron Yellow R 48, 055.

The resulting fabric shows loops of the inner inelastic fiber which is dyed maroon protruding randomly to the fabric surface, producing a fine slubby appearance with the contrast between the maroon inner fiber and the gold outer fiber. Such fabrics offer a wide range of styling potential depending on fiber choice and variations in the ratio of the two inelastic fibers. They are particularly suited for womens dresses and suits and also for sweaters. After hours of wear, a garment made from the above fabric is in good condition with the fabric surface showing a high degree of surface stability. The fabric has excellent bulk as a result of the elastomeric fiber contraction as well as the self-crimping composite fiber. The fabric has a three dimensional appearance.

Other combinations of inelastic fibers with spandex filament cores can be used to give unique color and luster contrasts and to modify the bulk of the fabrics. The fabric described above has a fabric weight of 13.9 ounces per square yard (465 grams per square meter) and a bulk of 6.2 cc./gm.

EXAMPLE II Sliver B of Example I is core-spun with 40 denier spandex continuous filament fiber and the resulting corespun yarn is further core-spun in the opposite direction with Sliver A of Example I. A fabric knit from this yarn and dyed as in Example I has a maroon surface with spots of gold showing through the surface. This fabric has a weight of 14.3 ounces per square yard (479 grams per square meter) and a bulk of 6.4 cc./ gm.

The yarns may be stretched at some stages of the operations and may also be heat-set at some stages. These variations make it possible to vary the limit of stretch of the fabric, the stretch modulus, and the bulk of the final yarn. Thus, the spandex yarn may be partially stretched and heat-set prior to Spinning. Alternatively, it may be stretched and spun under tension to the first corespun yarn and this yarn heat-set before carrying out the final core-spinning. Or, the first core-spun yarn can be further core-spun under tension Without heat-setting and the final yarn then heat-set.

The yarns of this invention may be converted to fabrics by weaving or by knitting. They are highly suitable for knitting because of the desirable limited stretch and low stretch modulus. If the first and second inelastic fibers have different dyeing properties, then cross-dyeing will be possible. The resulting yarns will be bulky due to the contraction of the elastic fiber and can be made of even greater bulk by using blends of inelastic fibers of different shrinkage or by using self-crimping fibers in one or both sheaths. Furthermore, by proper selection of the amount of twist provided in the second core-spinning, a balanced yarn can be obtained with little tendency to untwist (whether or not the yarn is heat-set).

What is claimed is:

1. An elastic core-on-core spun yarn comprising:

an initially stretched elastic core of at least one elastic continuous filament,

a first core-spun sheath consisting of inelastic staple fiber roving (I) surrounding the said core in a series of turns, and

a second core-spun sheath consisting of inelastic staple fiber roving (II) surrounding the said core and portions of said first sheath in a series of turns of opposite spiral disposition to that of the said turns of said roving (I).

2. The elastic yarn claim 1 wherein the said inelastic staple fibers of the said rovings (I) and (II) have different dyeability properties, and at least some of said turns of said first sheath protrude and come through the surface of the said second sheath.

3. The elastic yarn of claim 1 wherein the series of turns of said roving (I) and (II) are each between 3 and turns per inch.

4. The elastic yarn of claim 3 wherein the series of turns of said rovings (I) and (II) are essentially equal in number of turns per inch.

5. The elastic yarn of claim 1 wherein said elastic continuous filament is a segmented elastomer.

6. The elastic yarn of claim 1 wherein said inelastic staple fibers in roving (I) and (II) are selected from the group consisting of acrylic and modacrylic fibers.

7. The elastic yarn of claim 1 wherein said elastic core comprises about 0.5 to about 10.0 percent by weight of the said elastic yarn and wherein the said first and second sheaths comprise essentially equal proportions of the balance of said elastic yarn,

8. A fabric of the elastic yarn of claim 1.

9. The process for producing an elastic yarn comprisrng:

stretching an elastic core of at least one elastic continuous filament,

first core-spinning the stretched core with first inelastic staple fiber roving (I) to provide a yarn having series of turns of said roving (I) around said core, and thereafter second core-spinning the core-spun yarn with inelastic staple fiber roving (II) to provide a series of turns of said roving (II) around said core and portions of said roving (I); said turns of said roving (II) be ing of the opposite spiral disposition compared to the direction of the turns of said roving (I).

10. The process of claim 9 wherein said stretching is between about and about 450% said first corespinning provides from about 6 to about 20 turns per inch twist, and said second core-spinning provides from about 3 to about 10 turns per inch twist.

11. The process of claim 10 wherein said first corespinning provides about 12 Z turns per inch twist and said second core-spinning provides about 6 S turns per inch twist.

References Cited UNITED STATES PATENTS 2,302,543 11/1942 Gift et a1. 57163 XR 2,587,117 2/1952 Clay 57l52 3,166,885 1/1965 Bridgeman et al. 57-152 3,234,724 2/1966 Storti 57-152 3,306,081 2/1967 Miles et a1 57163 XR 3,344,597 10/1967 Petree 57l57 2,076,270 4/1937 Harris 57-163 2,076,271 4/1937 Harris 57--163 XR 2,076,273 4/1937 Harris 57163 XR 3,257,793 6/1966 Abbott 57163 3,308,615 3/1967 Susskind et al. 57163 XR 3,380,244 4/1968 Martin 57l52 JOHN PETRAKES, Primary Examiner US. Cl. X.R. 57-163 

